Crankcase vent valve



Oct. 2, 1962 H. H. DIETRICH CRANKCASE VENT VALVE Filed June 15, 1960 2'-1 u ..1 LL

LLI U) 0 2 [I U I I I l I I8 15 I2 9 INVENYZOR.

MANIFOLD VACUUM Zdarafiflze/rzcfi ATTORNEY United States Patent Ofiice3,056,420 Patented Oct. 2, 1962 3,056,420 CRANKtZASE VENT VALVE HowardH. Dietrich, Rochester, N.Y., assignor to General Motors Corporation,Detroit, Mich., a corporation of Delaware Filed June 15, 1968, Ser. No.36,240 5 Claims. (Cl. 137-245) The present invention relates to a valvedevice for venting or drawing off fuel vapors from an internalcombustion engine crankcase and redirecting them into the intakemanifold whereby they will subsequently be consumed during thecombination cycle of the engine. Valves of this type are generally oldand function to draw off such fuel vapors in accordance with variationsin manifold vacuum. More specifically, the present invention relates toan improved crankcase vent valve in which a non-clogging feature hasbeen added.

Crankcase ventilating valves of the general type involved are importantas means for eliminating one source of unburned fuels which have beenvented to the atmosphere in the past. The present vent valve insures theconsumption of crankcase gases by the engine and avoids their beingdischarged into the atmosphere.

The details as well as other objects and advantages of the presentinvention will be apparent from a perusal of the detailed descriptionwhich follows.

In the drawings:

FIGURE 1 is a diagrammatic representation of the subject vent valvecooperating with an internal combustion engine; and

FIGURE 2 is a graph showing the general relationship of crankcase airflow to manifold vacuum.

Referring to FIGURE 1, an internal combustion engine is shown generallyat including a carburetor 12 mounted on an intake manifold 14, acrankcase 15 and an oil pan 16. During normal engine operation a certainamount of the combustion gases are blown by the engine cylinder pistonrings into the crankcase. In the past, crankcases have been openlyvented, usually through the crankcase filler pipe, whereby the blow-bygases have been discharged to the atmosphere and thereby contributing tothe contamination of the latter.

In the present invention, a vent valve device 18 is provided wherebycrankcase gases are adapted to be drawn into intake maniiold 14 andsubsequently consumed during the normal combustion cycle of the engine.Vent valve device 18 includes a pair of easing members 20 and 22peripherally clamping a diaphragm 24 therebetween. In the presentinstance, diaphragm 24 is made of metal and actually provides a springforce the purpose of which will subsequently be considered. To permitadequate fiex ing a plurality of concentric annular rings or folds 26are formed in diaphragm 24.

A central opening is provided in casing 20 and adapted to threadablyreceive a tube 28 which is open at one end and communicates at its otherend through a conduit 30 with crankcase 15. The open end of tube 28terminates adjacent the flattened center portion 32 of diaphragm 24. Thespring construction of diaphragm 24 is such that it is urged away fromthe open end of tube 28 thereby tending to communicate chamber 34defined by diaphragm 24 and casing 20 with the tube. A second tube 36extends through a second opening provided in casing 20. Tube 36communicates with intake manifold 14 through a conduit 37. Thus bothtubes 28 and 36 are adapted to communicate with chamber 34 and therebycause air to flow from crankcase 15 to intake manifold 14.

A central opening is provided in casing 22 and is adapted to threadablyreceive an adjusting screw 38. Adjusting screw 38 provides a seat forone end of a spring 40 the other end of which biases against centralportion 32 of diaphragm 24. By adjusting screw 38, the resultant springactuation of the metal diaphragm 24 may be varied to vary crankcase airflow. A second hole 42 is provided in casing 22 and communicates chamber44 defined by casing 22 and diaphragm 24 to the atmosphere.

Upon a decrease in manifold vacuum the spring force of diaphragm 24 willuncover the open end of tube 28 permitting manifold vacuum to drawcrankcase gases through the open end of tube 28 and out of tube 36 tointake manifold 14. On the other hand, during conditions of highmanifold vacuum, as occurs during light engine loads, the vacuum forceacting on the right side of diaphragm 24 will move center portion 32 ofthe diaphragm to block the open end of tube 28. However, to insure apredetermined amount of crankcase ventilation even under high vacuumconditions, a slot 46 is formed in tube 28 which provides a desired lowvalue of crankcase venting since blow-by is low at light engine load andlittle air flow is required. Also at idle total air flow into the engineis low, e.g., 6 c.f.m. most of which should go through the carburetorfor proper i-dle operation of engine.

Referring to FIGURE 2, a curve is indicated showing the relationshipbetween crankcase air flow and manifold vacuum. The curve indicates arelatively flat portion A representing the constant air flow conditionwhich occurs when diaphragm 24 closes the open end of tube 28. Underthis condition crankcase air flow is limited to that amount which passesthrough slot 46. Portion B of the curve illustrates that as manifolddepression decreases diaphragm 24 progressively uncovers the open end oftube 28 thereby increasing the quantity of air flow through thecrankcase.

The present device insures the minimum air flow represented by portion Aof the curve of FIGURE 2 even when manifold vacuum is suificiently highto block the open end of tube 28.

Inasmuch as crankcase gases contain particles of oil and otherimpurities, over a period of time slot or fixed orifice 46 can becomeclogged thereby reducing or entirely eliminating crankcase air flowunder the high manifold vacuum conditions noted. To prevent thisoccurrence a hairpin like spring wire 48 is provided. One end of wire 48is fixed to tube 28 while the other end is free and biases againstcentral portion 32 of diaphragm 24. Thus as diaphragm 24 flexes, wire 48is moved longitudinally back and forth through slot 46 therebycontinuously cleaning the same and leaving it free of any foulingmaterial. The spring force of wire 48 is negligible and is not intendedto in any way affect the spring function of diaphragm 24.

I claim:

1. An engine crankcase vent valve comprising first and second casingmembers, a resilient diaphragm peripherally clamped between said casingmembers, a first tube centrally supported by one of said casing membersand terminating in an open end disposed proximate said diaphragm, avacuum chamber defined by said diaphragm and said one casing member, asecond tube mounted in said one casing member and openly communicatingwith said chamber, said first tube having an engine crankcaseconnection, said second tube having an engine intake manifold connectionwhereby when said engine crankcase connection is made to an enginecrankcase and said intake manifold connection is made to an engineintake manifold crankcase gases may be drawn through said first tube,said chamber and said second tube to be discharged into an engine intakemanifold said diaphragm being adapted to be moved under the influence ofengine manifold vacuum to block the open end of said first tube againstthe resilient force of said diaphragm, a slot formed in said first tubeand openly communicating with said chamber under all operatingconditions, and means operated by said diaphragm to clear said slot ofany impurities tending to collect therein.

2. A crankcase vent valve as set forth in claim 1 which includes meansfor adjusting the resilience of said diaphragm.

3. A crankcase vent valve as set forth in claim 1 in which said slotcleaning means includes a hairpin like wire member fixed at one end tosaid first tube and having its other end projecting through said slotand engaging said diaphragm whereby movement of the diaphragm will causesaid other end to move through said slot.

4. A crankcase vent valve as set forth in claim 2 in which the means foradjusting the diaphragm comprises a screw member threadably supported inthe other of said casing members and a spring member biasing betweensaid adjustable screw and said diaphragm.

5. A crankcase vent valve as set forth in claim 1 in which saidresilient diaphragm comprises a thin metallic member having a flatcentral portion and a plurality of concentrically related annular folds.

References Cited in the file of this patent UNITED STATES PATENTS 102,592,380 Beckett Apr. 8, 1952 2,716,398 McMullen Aug. 30, 19552,742,057 Krieck Apr. 17, 1956 2,884,950 Settelmayer et 'al May 5, 1959l I I l

